JP2003225716A - Hydraulic forming method and hydraulically formed cylindrical member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide hydraulic forming method by which the damage of joints is suppressed even in the case that the degree of tube expansion is large and the degree of tube expansion in the parts other than the joints of the expanded tube parts is raised and a hydraulically formed cylindrical member. <P>SOLUTION: A tube stock having hollow chambers is formed by forming the joints 21, 22 by joining the end faces in the axial direction of the cylindrical members in series. By increasing the internal pressure of the hollow chambers of the tube stock in the state where the tube stock is arranged in the cavity of a forming die, the expanded parts 40 are formed by expanding the peripheral walls in the parts having at least the joints 21, 22 of the tube stock. The peripheral outer lengths of the joints 21, 22 of the expanded tube parts 40 are set shorter than the peripheral outer lengths of the other parts other than the joints 21, 22 of the expanded tube parts 40. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydroform method for molding with a fluid pressure of water or the like, and a hydrofoam tubular member molded by the hydroform method. The present invention can be applied to, for example, a structural member such as a reinforcing member that reinforces the vehicle body.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 11-179441 discloses
A technique is disclosed in which a bulging device (corresponding to a hydroform device) is used to expand a peripheral wall of a pipe material having a joint in which ends are joined in series together with the joint by fluid pressure. According to this technique, in the state where the end faces of two pipe materials are joined in series to form a seam, high pressure is applied in a direction opposite to each other along the axial direction of the pipe materials by a pressure press. A fluid pressure is applied from the fluid supply pipe to the hollow chamber of the pipe material to expand the peripheral wall of the pipe material. At the time of pipe expansion, a pipe material having a relatively thin wall is more likely to stretch than a pipe material having a relatively thick wall, and therefore the peripheral wall may be broken. Therefore, according to the above-mentioned publication technique, a fracture preventing block that restrains the deformation of the peripheral wall of the pipe material having a relatively thin wall and a support block that restrains the deformation of the peripheral wall of the pipe material having a relatively thick wall are provided. By providing and controlling each block individually when expanding the pipe, the peripheral wall of the pipe material having a relatively thick wall and the peripheral wall of the pipe material having a relatively thin wall are expanded at substantially the same time.

[0003]

According to the technique disclosed in the above publication, although the breakage of the peripheral wall of the pipe material having a relatively small wall thickness can be suppressed, when the pipe material has a large degree of expansion,
The pipe material seam may be damaged. Therefore, there is a limit to the increase in the degree of pipe expansion of the pipe material.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to suppress damage to a joint even when the degree of pipe expansion is large, and to enhance the degree of pipe expansion of a portion other than the joint of the pipe expanding portion. An object of the present invention is to provide a hydrofoam method and a hydrofoam tubular member capable of performing the above.

[0005]

In the hydroforming method according to the present invention, an axial pipe having a hollow chamber is formed by joining axial end faces of at least two tubular members in series to form a joint. A joining step, an arranging step of arranging the raw pipe in the cavity of the molding die, and increasing the internal pressure of the hollow chamber of the raw pipe to expand the peripheral wall of at least the portion having the seam of the raw pipe. In the hydroforming method of performing a pipe expanding step of forming a pipe expanding portion by abutting on the cavity mold surface of the molding die, the pipe expanding step, the outer peripheral length of the joint of the pipe expanding portion,
It is characterized in that it includes an operation of setting the outer peripheral length of the pipe expanding portion other than the seam other than the seam.

According to the hydroforming method of the present invention, in the pipe expanding step, the outer peripheral length of the joint of the pipe expanding portion is set to be shorter than the outer peripheral length of the portion of the pipe expanding portion other than the joint. Therefore, even when the degree of pipe expansion is large in the pipe expanding step, the load acting on the joint is reduced.

The hydroformed tubular member according to the present invention has a hollow chamber formed by joining the axial end faces of at least two tubular members in series to form a joint, and is formed by the hydroforming method. In the member, the outer peripheral length of the joint is set to be shorter than the outer peripheral length of the expanded pipe portion other than the joint.

According to the hydrofoam tubular member of the present invention, the outer peripheral length of the joint of the expanded pipe portion is set shorter than the outer peripheral length of the other portion of the expanded pipe portion other than the joint. Therefore, even when the degree of pipe expansion is large in the pipe expanding step, the load acting on the joint is reduced.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the tube expanding step, the internal pressure of the hollow chamber of the tube is increased to expand the peripheral wall of at least the seam portion of the tube, and the expanded peripheral wall is used as a cavity mold surface of the molding die. To form a pipe expansion part. The internal pressure can be increased by feeding a fluid to the hollow chamber of the raw pipe. As the fluid, a liquid such as water or oil can be adopted. As the material of the raw pipe, various metals such as iron-based, aluminum-based, magnesium-based, titanium-based, and copper-based can be adopted, but the material is not limited to these. The iron system may be an alloy steel system such as stainless steel, a carbon steel system, a pure iron system, a hypoeutectoid steel system, a eutectoid steel system, a hypereutectoid steel system, or a ferrite structure- Pearlite, ferrite, austenite, bainite,
It may be a sorbite type.

The cavity die surface of the forming die has a protruding portion that protrudes toward the inside of the cavity. As an operation performed in the tube expanding process, the seam of the raw pipe is brought into contact with the protruding portion of the forming die cavity surface. By doing so, it is possible to adopt a mode in which the pipe expansion amount of the joint is suppressed.

The shell is formed by joining the shaft end faces of at least two tubular members in series to form a joint. The raw tube may have a cylindrical shape or a rectangular tube shape. Therefore, as the tubular member, a form having a first tubular member and a second tubular member joined in series to the first tubular member can be adopted. Further, as the tubular member, a first tubular member, a second tubular member joined in series to the first tubular member, and a third tubular member joined in series to the second tubular member. Can be adopted. Joining the seam may be done by welding. Well-known welding can be adopted as the welding, but a means for irradiating a high-energy beam at the joint of the raw pipe to perform welding, or a friction welding means for performing friction welding can be adopted. A laser beam and an electron beam are typical high energy beams.

It is preferable that the adjacent tubular members constituting the raw pipe have different characteristics from each other. As a characteristic,
It may be at least one of strength, hardness, plastic deformability, wall thickness, and composition. In this case, the strength of the tubular member located in the central region in the axial direction of the raw pipe can be made higher than the strength of the tubular member located in the end region in the axial direction of the raw pipe. Further, the hardness of the tubular member located in the central region in the axial direction of the raw pipe can be made higher than the hardness of the tubular member located in the end region in the axial direction of the raw pipe. Further, the plastic deformability of the tubular member located in the central region in the axial direction of the raw pipe can be made larger than the plastic deformability of the tubular member located in the end region in the axial direction of the raw pipe. Further, the wall thickness of the tubular member located in the central region in the axial direction of the base pipe can be made larger than the wall thickness of the tubular member located in the end region in the axial direction of the base pipe.

As described above, as the tube, the first tubular member, the second tubular member joined in series to the first tubular member, and the first tubular member joined in series to the second tubular member. A configuration having three tubular members can be adopted. In this case, the strength of one or two of the first tubular member, the second tubular member, and the third tubular member can be made higher than the strength of the remaining tubular members. Further, the hardness of one or two of the first tubular member, the second tubular member, and the third tubular member can be made higher than the hardness of the remaining tubular members.
Further, the plastic deformability of one or two of the first tubular member, the second tubular member, and the third tubular member can be made larger than the plastic deformability of the remaining tubular members. Further, the wall thickness of one or two of the first tubular member, the second tubular member, and the third tubular member can be made larger than the wall thickness of the remaining tubular members.

Alternatively, the strength of the second tubular member can be made higher than the strength of one or both of the first tubular member and the third tubular member. Further, the hardness of the second tubular member can be made higher than the hardness of one or both of the first tubular member and the third tubular member. Further, the plastic deformability of the second tubular member can be made larger than the plastic deformability of one or both of the first tubular member and the third tubular member. The wall thickness of the second tubular member is set to the first tubular member and the third tubular member.
It can be thicker than the wall thickness of one or both of the tubular members.
The carbon content of the second tubular member can be made higher than the carbon content of one or both of the first tubular member and the third tubular member.

As a raw pipe, a first tubular member, a second tubular member joined in series to the first tubular member, and a third tubular member joined in series to the second tubular member. When the form having is adopted, the following can be done. For example, the first
The tensile strength of the tubular member and the third tubular member can be relatively low, and the tensile strength of the second tubular member can be relatively high. Therefore,
The first tubular member and the third tubular member are, for example, 300 to 400M.
A form formed of a steel material having a tensile strength of Pa can be adopted. The second tubular member is, for example, 420 to 800 MPa.
It is possible to adopt a form formed of a steel material having a tensile strength of. The carbon content of the first tubular member and the third tubular member can be relatively low, and the carbon content of the second tubular member can be relatively high. Therefore, as the first tubular member and the third tubular member, it is possible to adopt a mode in which the carbon content is formed of a steel material having a carbon content of, for example, about 0.08 to 0.14 wt%. As the second tubular member, it is possible to adopt a mode in which the carbon content is formed of a steel material having a carbon content of, for example, about 0.17 to 0.4 wt%.

As an operation for shortening the outer peripheral length of the seam, the cross-sectional area of the seam of the expanded pipe portion (including the cross-sectional area of the hollow portion defined by the inner wall surface of the seam) is other than the seam of the expanded pipe portion. It is possible to employ a mode in which the cross section is smaller than the cross sectional area of the portion (including the cross sectional area of the hollow portion defined by the inner wall surface of the other portion). In this case, it is possible to adopt a mode in which a groove is formed on the outer circumference of the joint of the expanded pipe portion. Further, in the case where a corner area exists at the seam of the expanded tube portion, it is possible to adopt a mode in which the chamfered portion is formed in the corner area. Further, the radius of curvature of the arc that defines the contour of the corner area of the seam of the expanded pipe is larger than the radius of curvature of the arc that defines the contour of the corner area of the expanded pipe other than the seam. Can also be adopted.

When the hydroform tubular member is formed by expanding the raw pipe, the joint may be expanded, or the joint may not be expanded or substantially not expanded.

A plurality of seams are provided in the axial direction, and the outer circumference of at least one seam may have a value different from the outer circumferences of other seams. In this case, as will be described later, when the seam functions as a crash bead for shock absorption, the shock absorption can be prioritized.

The hydroformed tubular member formed by the hydroforming method may have a cylindrical shape or a rectangular tubular shape. The hydrofoam tubular member can be applied to a structure. In particular, it can be applied to a reinforcing member that reinforces the vehicle body. Examples of the reinforcing member include a front side member that reinforces a side portion of a vehicle front portion, a center pillar between a front seat and a rear seat of the vehicle, a center pillar reinforce that reinforces the center pillar, a roof side member, and the like. .

[0020]

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a raw tube 1 before being formed by the hydroforming method. FIG. 2 shows a cross section of the main part of the raw pipe 1 before being formed by the hydroforming method. FIG. 3 shows a hydroform tubular member 4 formed by expanding the pipe by the hydroform method. As shown in FIG. 3, the expanded portion 40 of the hydrofoam tubular member 4 has a rectangular tubular shape.

In the joining step according to this embodiment, as shown in FIG. 1, the iron-based first tubular member 11, the iron-based second tubular member 12, and the iron-based third tubular member 13 are connected in series. Welded to
A blank tube 1 having a hollow chamber 1x is formed. The raw tube 1 has a long tubular shape and has the same outer diameter in the axial direction. The second tubular member 12 is arranged between the first tubular member 11 and the third tubular member 13. As shown in FIG. 2, the first tubular member 1
The shaft end surface 11c of the other end portion of 1 and the shaft end surface 12c of the one end portion of the second tubular member 12 are joined in a butt state by welding to form a first joint 21. Second tubular member 12
The shaft end surface 12d at the other end and the shaft end surface 13c at the one end of the third tubular member 13 are joined in a butt state by welding to form a second joint 22. 21x and 22x show welded parts. The first seam 21 and the second seam 2
2 are along the axis-perpendicular direction, and are arranged in series at a predetermined interval in the axial direction of the shell 1.

In welding, a laser beam which is a high-energy beam is irradiated along the circumferential direction of the first seam 21 and the second seam 22 without laminating the overlay layers, and the first seam 21 and the second seam 22 are welded. Laser beam welding (high-energy beam welding) is used to partially melt and then solidify. In addition, according to the laser beam welding, a quenching region may be locally formed in the first joint 21 and the second joint 22.

The characteristics of the first to third tubular members 11 to 13 adjacent to each other are different from each other. That is,
The strength of the steel material forming the second tubular member 12 is higher than the strength of the steel material forming the first tubular member 11 and the third tubular member 13. Therefore, the intermediate region in the axial direction of the raw tube 1 has high strength. Specifically, the first tubular member 1
The first and third tubular members 13 are made of steel having a relatively low tensile strength (for example, 300 to 500 MPa). The second tubular member 12 arranged in the central region in the axial direction has a relatively high tensile strength (for example, 520 to 800).
(MPa). The first tubular member 11 and the third tubular member 13 are ferrite-perlite-based or ferrite-based, and are made of steel material having a relatively low carbon content (for example, about 0.08 to 0.14 wt%). There is. Second located in the central region in the axial direction
The tubular member 12 is a ferrite-perlite system and has a relatively high carbon content (for example, 0.17 to 0.4 wt%).
It is made of steel.

Further, the wall thickness t2 of the steel material constituting the second tubular member 12 is made larger than the wall thickness t1 of the first tubular member 11 and the wall thickness t3 of the steel material constituting the third tubular member 13. There is. However, in the raw pipe 1 before being formed by the hydroforming method, the outer peripheral surface 12o of the second tubular member 12, the outer peripheral surface 11o of the first tubular member 11, and the outer peripheral surface 13o of the third tubular member 13 are formed.
Are flat with no step. Therefore, as shown in FIG. 2, the inner peripheral surface 12i of the second cylindrical member 12 is the inner peripheral surface 11i of the first cylindrical member 11 and the inner peripheral surface 1 of the third cylindrical member 13.
It projects radially inward from 3i.

As shown in FIG. 4, the cavity die surface 30 of the molding die 3 is formed with a first protrusion 31 which projects inward of the cavity 3c of the molding die 3. The first protruding portion 31 makes one round around the outer circumference of the raw tube 1, and has a convex surface 31a.
This is for forming a groove 51 (see FIG. 3) described later by suppressing the amount of expansion of the raw tube 1 in the radially outward direction. Further, as shown in FIG. 5, the cavity mold surface 30 of the molding die 3 is formed with a second protrusion 32 that projects toward the inside of the molding cavity 3c of the molding die 3.
The second protruding portion 32 faces the outer circumference of the raw tube 1,
This is for forming a chamfered portion 52 (see FIG. 3) described later by suppressing the amount of expansion of the corner area 40x of the expansion portion 40 of the base pipe 1 in the radially outward direction.

As shown in FIG. 6, the molding die 3 is composed of a first separation mold 3a and a second separation mold 3b, and the molding cavity 3c has a substantially rectangular cross section. Therefore, the cavity mold surface 30 of the molding die 3 has a cavity mold surface 30h extending in the horizontal direction and a cavity mold surface 30v extending in the vertical direction. In the arranging step, the raw pipe 1 is arranged in the molding cavity 3c of the metal molding die 3. In the arranging step, although not shown, a water feeding device having water feeding ability is set on the shaft end portion of the raw pipe 1.

Next, a pipe expanding step is performed in which water is fed from the water feeding device to the hollow chamber 1x of the raw pipe 1 to increase the internal pressure of the hollow chamber 1x of the raw pipe 1. As a result, as shown in FIGS. 6 to 8, the peripheral wall of the raw tube 1 is radially expanded and gradually expanded.
Then, the expanded peripheral wall is brought into contact with the cavity mold surface 30 of the molding die 3. Since the molding cavity 3c of the molding die 3 has a substantially rectangular cross section, the expanded tube portion 40 is
c, and the cross-sectional shape of the expanded tube portion 40 becomes substantially square, and the hydroformed tubular member 4 is molded.
Generally, during molding, as shown in FIG. 7, the central region 30 m of the outer peripheral surface of the blank tube 1 and the cavity mold surface 30 of the molding die 3 is
Has priority contact with. The contact between the outer peripheral surface of the raw tube 1 and the corner portion 30n of the cavity mold surface 30 of the molding die 3 is the final stage of molding by the hydroforming method. In the forming by the corner portion 30n at the end of forming by the hydroforming method, when the forming load is large and the degree of pipe expansion is high, the corner region 4 of the base pipe 1 is formed.
There is a risk of damage to the 0x part. In this way, the corner area 40x at the end of molding by the hydroforming method
As will be described later, it is effective to form the chamfered portion 52 and suppress the expansion amount of the corner area 40x more than other portions.

As shown in FIG. 3, the expanded portion 40 of the hydroformed tubular member 4 formed by the hydroforming method has a rectangular tubular shape, and has a surface 40h along the lateral direction and a surface 40v along the longitudinal direction. And a corner area 40x. First
Since the joint 21 and the second joint 22 are located in the pipe expanding portion 40, the first joint 21 and the second joint 22 are also expanded. The groove 5 is formed on the outer periphery of the first joint 21 of the expanded pipe portion 40.
1 is formed, the expansion amount of the first joint 21 is suppressed as compared with the other portions. The groove 51 is the expanded portion 40.
Are continuous along the circumferential direction.

Further, as shown in FIG. 3, chamfered portions 52 are formed in the four corner regions 40x of the second joint 22 of the expanded portion 40 of the hydroformed tubular member 4 formed by the hydroforming method. ing. The chamfered portion 52 has slopes 52a facing each other. Since the chamfered portion 52 is formed on the outer circumference of the second joint 22 of the pipe expanding portion 40, the pipe expanding amount of the chamfered portion 52 is suppressed as compared with other portions.

When the hydroformed tubular member 4 is used, the cut surface 10 is finally removed in order to remove both axial end portions 4p in the axial direction of the hydroformed tubular member 4.
Cut along 0. The hydrofoam tubular member 4
The shaft end 4p of is not expanded.

FIG. 9 shows a cross section of a portion of the expanded tube portion 40 of the hydrofoam tubular member 4 other than the first joint 21 and the second joint 22. The first joint 21 of the expanded portion 40
The outer peripheral length of the portion other than the second joint 22 along the cross-sectional direction is indicated as L3. The first of the expanded section 40
The cross-sectional area (A3 × B3) of the portion other than the joint 21 and the second joint 22 includes the area of the hollow portion formed by the inner wall surface of the pipe expanding portion 40, and is shown as S3.

The first seam 21 is shown in FIG. 10 (A).
This will be described with reference to (B). FIG. 10A shows the molding die 3.
2 shows a state in which the pipe expansion amount of the pipe expanding portion 40 is suppressed by the first projecting portion 31, and the groove 51 is formed on the outer circumference of the first joint 21 of the pipe expanding portion 40 by the first projecting portion 31. FIG. 10 (B) shows a cross section of the expanded tube portion 40 of the hydrofoam tubular member 4 having the groove 51. As shown in FIGS. 10A and 10B, as described above, the groove 51 is formed on the outer periphery of the first joint 21 of the expanded portion 40 of the hydrofoam tubular member 4, and the groove 5 is formed.
1 is molded by the first protruding portion 31 of the molding die 3. Expansion part 4
The outer peripheral length along the cross-sectional direction of the first seam 21 in which the groove 51 is formed is shown as L1. According to this embodiment, the outer peripheral length L1 is set shorter than the outer peripheral length L3 described above (L1 <L3). Therefore, the groove 51 can function as a peripheral length shortening portion. The cross-sectional area of the first joint 21 of the expanded portion 40 of the hydrofoam tubular member 4 (A
1 × B1) is shown as S1. The cross-sectional area S1 is set smaller than the above-mentioned cross-sectional area S3 (S1
<S3). The cross-sectional area of the first joint 21 (A1 x B1)
As is clear from FIG. 10 (B), includes the area of the hollow portion defined by the inner wall surface of the first joint 21 in the expanded portion 40 of the hydrofoam tubular member 4.

The second joint 22 is shown in FIG. 11 (A).
This will be described with reference to (B). FIG. 11A shows that the tube expansion amount of the tube expansion portion 40 of the hydrofoam tubular member 4 is suppressed by the second protrusion 32 of the molding die 3, and the corner area 40 of the tube expansion portion 40 is shown.
A state in which the chamfered portion 52 is formed is shown at x. Figure 11
(B) shows a cross section of the expanded tube portion 40 of the hydrofoam tubular member 4 having the chamfered portion 52 in the corner region 40x. Figure 1
As shown in FIGS. 1 (A) and 1 (B), a chamfered portion 52 is formed in a corner region 40x of the second joint 22 of the expanded tube portion 40 of the hydrofoam tubular member 4, and the chamfered portion 52 is formed. It is molded by the second protrusion 32 of the mold 3. Chamfered part 5
The slope 52a of No. 2 is the surface 40 of the expanded tube portion 40 having a substantially rectangular tube shape.
It is inclined with respect to h and the surface 40v.

When the chamfered portion 52 is not formed on the hydrofoam tubular member 4, as shown in FIG. 11 (C), the outer peripheral length L2 of the second joint 22 portion is the side length m1 and the side length m2. Including. However, the hydrofoam tubular member 4
When the chamfered portion 52 is formed in the corner region 40x of the expanded pipe portion 40, the outer peripheral length L2 of the second joint 22 is
It does not include the side length m1 and the side length m2, but includes the side length m3. The side length m3 is shorter than the side length m1 + the side length m2. Ignoring the rounded arcs of the corner area 40x of the expanded section 40, m3
^{This is because 2} = m1 ² + m2 ² .

As described above, the second joint 22 and the first joint 2 of the expanded portion 40 of the hydrofoam tubular member 4 are used.
The outer peripheral length of the portion other than 1 along the cross-sectional direction is indicated as L3. As shown in FIG. 11B, the outer peripheral length of the expanded portion 40 of the hydrofoam tubular member 4 along the cross-sectional direction of the second joint 22 is indicated as L2.
According to this embodiment, since the chamfered portion 52 is formed on the hydrofoam tubular member 4, the outer peripheral length L2 is set shorter than the outer peripheral length L3 (L2 <L3). Therefore, the chamfered portion 52 can function as an outer peripheral length shortening portion.

As described above, according to this embodiment, the outer peripheral length L of the first joint 21 of the hydrofoam tubular member 4 is L.
1 is set to be shorter than the outer peripheral length L3 of the portion other than the first seam 21 of the expanded tube portion 40 of the hydrofoam tubular member 4. Further, the outer peripheral length L2 of the second joint 22 of the hydrofoam tubular member 4 is set to be shorter than the outer peripheral length L3 of the portion other than the second joint 22 of the pipe expanding portion 40 of the hydroform tubular member 4. . Therefore, even when the degree of pipe expansion of the hydrofoam tubular member 4 is large in the pipe expanding step, the first joint 21 and the second joint 2
The pipe expansion amount of 2 can be suppressed, and the load acting on the first joint 21 and the second joint 22 can be reduced. Therefore, the first joint 2 of the expanded portion 40 of the hydrofoam tubular member 4
It is possible to increase the degree of pipe expansion in the portions other than the first and second joints 22. As described above, according to the present embodiment, damage to the first joint 21 and the second joint 22 can be avoided even when the degree of pipe expansion of the pipe expansion portion 40 of the hydrofoam tubular member 4 is large.

According to this embodiment, the outer peripheral length L1 of the first joint 21 is different from the outer peripheral length L2 of the second joint 22. Therefore, as will be described later, when the groove 51 of the first joint 21 and the chamfered portion 52 of the second joint 22 function as a crash bead for impact absorption, it is possible to prioritize impact absorption.

Further, according to the raw tube 1 of this embodiment, the thickness t2 of the steel material forming the second tubular member 12 is the same as that of the first tubular member 1.
The thickness t1 is 1 and the thickness t3 of the steel material forming the third tubular member 13 is larger. Therefore, also in the hydroformed tubular member 4 obtained by expanding the raw pipe 1, the wall thickness of the second tubular member 12 arranged in the intermediate region in the axial direction is arranged in the end region in the axial direction. First tubular member 1
The wall thickness of No. 1 and the wall thickness of the third tubular member 13 are made larger. For this reason, it is possible to reduce the weight of the hydrofoam tubular member 4 while increasing the strength of the portion requiring strength.

Before carrying out the hydrofoam method,
If necessary, the first joint 21 and the second joint 2 of the base pipe 1
It is also possible to heat 2 to soften it.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG. The second embodiment is the first
The operation is basically performed under the same conditions as those of the embodiment, and basically the same effects are obtained. The difference will be mainly described below. Hydrofoam tubular member 4 according to the present embodiment
Grooves 51 are formed in both the first seam 21 and the second seam 22 of B. The groove 51 is continuous in the circumferential direction of the expanded tube portion 40.

Expanding portion 4 of hydrofoam tubular member 4B
Of 0, the outer peripheral length along the cross-sectional direction of the first joint 21 is
Shown as L1. Hydrofoam tubular member 4
The outer peripheral length of the expanded portion 40 of B along the cross-sectional direction of the second joint 22 is shown as L2 (L1≈L2, L
1 = L2). Expanding portion 4 of hydrofoam tubular member 4B
Of 0, the outer peripheral length along the cross-sectional direction other than the first seam 21 and the second seam 22 is indicated as L3. According to this embodiment, the outer peripheral length L1 and the outer peripheral length L2 are equal to the outer peripheral length L3.
Is set shorter than (L3> L1, L2).

Therefore, in the pipe expanding step, even when the pipe expanding portion 40 of the hydrofoam tubular member 4B has a large pipe expanding degree, the pipe expanding amount of the first joint 21 and the second joint 22 can be suppressed, and the first joint 21 and second joint 22
The load acting on is reduced. Therefore, the degree of pipe expansion of the pipe expansion portion 40 of the hydrofoam tubular member 4B can be increased. As described above, according to the present embodiment, damage to the first joint 21 and the second joint 22 can be avoided even when the degree of pipe expansion of the pipe expansion portion 40 of the hydrofoam tubular member 4B is large.

(Third Embodiment) The third embodiment of the present invention will be described below with reference to FIG. The third embodiment is the first
The operation is basically performed under the same conditions as those of the embodiment, and basically the same effects are obtained. The difference will be mainly described below. According to the hydrofoam tubular member 4C, the corner regions 40 of both the first joint 21 and the second joint 22 are formed.
A chamfered portion 52 is formed at each x. The outer peripheral length along the cross-sectional direction of the first seam 21 is shown as L1. The outer peripheral length of the second joint 22 along the cross-sectional direction is shown as L2 (L1≈L2, L1 = L
2). The outer peripheral length along the cross-sectional direction other than the first joint 21 and the second joint 22 in the expanded portion 40 of the hydrofoam tubular member 4C is indicated as L3. According to this embodiment, the outer peripheral length L1 and the outer peripheral length L2 are set shorter than the outer peripheral length L3 (L3> L1, L2).

Therefore, even when the degree of pipe expansion of the hydrofoam tubular member 4C is large in the pipe expanding step, the first
The pipe expansion amount of the joint 21 and the second joint 22 can be suppressed, and the load acting on the first joint 21 and the second joint 22 is reduced. Therefore, the degree of pipe expansion of the pipe expansion portion 40 of the hydrofoam tubular member 4C can be increased. As described above, according to the present embodiment, damage to the first joint 21 and the second joint 22 can be avoided even when the pipe expanding portion 40 of the hydrofoam tubular member 4C has a large pipe expanding degree.

(Fourth Embodiment) The fourth embodiment of the present invention will be described below with reference to FIG. The fourth embodiment is the first
The operation is basically performed under the same conditions as those of the embodiment, and basically the same effects are obtained. The difference will be mainly described below. In the operation according to the present embodiment, the radius of curvature R1 of the circular arc that defines the contour of the corner region 40x of the first joint 21 of the pipe expanding portion 40 of the hydrofoam tubular member 4D is set to the first joint 21 of the pipe expanding portion 40. It is performed by making the radius of curvature R2 of an arc defining the contour of the corner area 40x of the other portions larger than R2. The second joint 22 can have a similar structure.

(Fifth Embodiment) The fifth embodiment of the present invention will be described below with reference to FIG. The fifth embodiment is the first
The operation is basically performed under the same conditions as those of the embodiment, and basically the same effects are obtained. The difference will be mainly described below. Element tube 1E formed by hydroforming
Is configured by welding the first tubular member 11E, the second tubular member 12E, and the third tubular member 13E in series. Second
The wall thickness t2 of the steel material forming the tubular member 12E is the same as the wall thickness t1 of the first tubular member 11E and the wall thickness t3 of the steel material forming the third tubular member 13E. In the raw pipe 1E, the outer peripheral surface 12o of the second tubular member 12E, the outer peripheral surface 11o of the first tubular member 11E, and the outer peripheral surface 1 of the third tubular member 13E.
3o is in a flush state without a step. The inner peripheral surface 12i of the second cylindrical member 12E, the inner peripheral surface 11i of the first cylindrical member 11E, and the inner peripheral surface 13i of the third cylindrical member 13E are flush with each other.

In the present embodiment, the carbon content and strength of the steel material forming the second tubular member 12E is determined by the first tubular member 11E.
And the carbon content and strength of the steel material forming the third tubular member 13E are set higher. According to this embodiment,
This blank tube 1E is expanded by the hydroform method.

(Sixth Embodiment) The sixth embodiment of the present invention will be described below with reference to FIG. The sixth embodiment is the first
The operation is basically performed under the same conditions as those of the embodiment, and basically the same effects are obtained. The difference will be mainly described below. An elementary tube 1 having a hollow chamber 1x in which an iron-based first tubular member 11 and an iron-based second tubular member 12 are joined in series by welding.
Form F. This blank tube 1F is expanded by the hydroform method. The first seam 21 is friction welded.

(Seventh Embodiment) The seventh embodiment of the present invention will be described below with reference to FIG. The seventh embodiment is the first
The operation is basically performed under the same conditions as those of the embodiment, and basically the same effects are obtained. The difference will be mainly described below. The iron-based first tubular member 11, the iron-based second tubular member 12, the iron-based third tubular member 13, and the iron-based fourth tubular member 14 are welded in series to form a hollow chamber 1x. Tube with 1G
To form. This raw tube 1G is expanded by the hydroform method. The first seam 21, the second seam 22, and the third seam 23 are joined by electron beam welding.
x, 22x, 23x are formed.

(Eighth Embodiment) The eighth embodiment of the present invention will be described below with reference to FIG. The eighth embodiment is the first
The operation is basically performed under the same conditions as those of the embodiment, and basically the same effects are obtained. The difference will be mainly described below. A first tube member 11H having a rectangular tube shape, a second tube member 12H having a rectangular tube shape, and a third tube member 13H having a rectangular tube shape are joined in series by welding, and a hollow tube having a hollow chamber 1x 1H is formed. This blank tube 1H is expanded by the hydroform method. The first seam 21 and the second seam 22 are joined by laser beam welding.

(Ninth Embodiment) The ninth embodiment of the present invention will be described below with reference to FIG. The ninth embodiment is the first
The operation is basically performed under the same conditions as those of the embodiment, and basically the same effects are obtained. The difference will be mainly described below. The hydrofoam tubular member 4K includes a first tubular member 11K having a cylindrical shape, and a second tubular member 12K having a cylindrical shape joined in series to the first tubular member 11K.
It has the cylindrical third cylindrical member 13K joined in series to the second cylindrical member 12K. A groove 51K is formed in the first joint 21 between the first tubular member 11K and the second tubular member 12K.
Are formed. A groove 51M is formed in the second joint 22 between the second tubular member 12K and the third tubular member 13K. The groove 51K and the groove 51M are continuous in the circumferential direction. The outer peripheral length L1 of the first joint 21 is set to be shorter than the outer peripheral length L3 of other portions of the expanded tube portion 40 other than the joint. The outer peripheral length L2 of the second joint 22 of the hydroform tubular member 4K is set to be shorter than the outer peripheral length L3 of the portion of the expanded portion 40 of the hydroform tubular member 4K other than the joint.

(Application Example) FIG. 20 shows a case where the hydrofoam tubular member of the present invention is applied to the front side member 7 of a vehicle. The front side member 7 is the vehicle 2
00 functions as a reinforcing member for the front portion 210. In a vehicle collision or the like, an external force along the axial direction of the front side member 7 acts on the front side member 7. The outer peripheral length of the joint of the pipe expanding portion 40 is set to be shorter than the outer peripheral length of other portions of the pipe expanding portion 40 other than the first joint 21 and the second joint 22. Therefore, the first seam 21 and the second seam 22 can also be expected to function as a crush bead that deforms preferentially over other parts and exerts a shock absorbing action. This is advantageous for avoiding damage to important parts such as the engine.

When the front side member 7 is formed of the hydrofoam tubular member 4 shown in FIG. 3,
In the hydrofoam tubular member 4, it is possible to make a difference in strength between the first joint 21 in which the groove 51 is formed and the second joint 22 in which the chamfered portion 52 is formed. Therefore, in the event of a vehicle collision, the front side member 7
You can prioritize damages when they are damaged and absorb shock.

(Others) According to the above-mentioned embodiment, the groove 5
Although 1 is continuous along the circumferential direction of the pipe expanding portion 40, the present invention is not limited to this, and the groove 51 may be discontinuous along the circumferential direction of the pipe expanding portion 40. According to the above-described embodiment, the chamfered portions 52 are formed in the four corner regions 40x of the second joint 22 of the expanded tube portion 40 of the hydrofoam tubular member 4, respectively. The chamfered portions 52 may be formed in three of the partial regions 40x. Alternatively, the chamfered portions 52 may be formed on only two or one of the four corner regions 40x. Besides, the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications within the scope not departing from the gist.

The following technical idea can be understood from the above description. (Additional Item 1) A joining step of forming an elementary tube having a hollow chamber by joining axial end surfaces of at least two tubular members in series to form a joint, and the elementary tube in a cavity of a molding die. Arranging step and increasing the internal pressure of the hollow chamber of the raw pipe, thereby expanding the peripheral wall of at least the portion having the seam of the raw pipe and bringing it into contact with the cavity mold surface of the molding die. In the method for manufacturing a front side member that performs a pipe expanding step of forming a pipe expanding portion, the pipe expanding step includes the outer peripheral length of the joint of the pipe expanding portion, and the outer peripheral length of the pipe expanding portion other than the joint. A method for manufacturing a front side member, comprising an operation of setting the length shorter than the outer peripheral length. In this case, since the load acting on the joint is reduced, damage to the joint can be avoided and the degree of pipe expansion of the portion of the pipe expansion portion other than the joint can be increased. (Additional Item 2) In a front side member formed by a hydroforming method, having a hollow chamber in which axial end surfaces of at least two tubular members are joined in series to form a joint, the outer peripheral length of the joint is A front side member characterized by being set shorter than the outer peripheral length of the expanded portion other than the seam. In this case, since the load acting on the joint is reduced, damage to the joint can be avoided and the degree of pipe expansion of the portion of the pipe expansion portion other than the joint can be increased. (Additional Item 3) In claim 10, a plurality of seams are provided in the axial direction, and the outer peripheral length of each seam is different from the outer peripheral lengths of other seams. Cylindrical member. When the seam acts as a crash bead, shock absorption can be prioritized. (Additional Item 4) The hydroformed tubular member according to claim 10, wherein an outer peripheral length shortening portion is provided on the outer periphery of the joint.

[0056]

According to the hydroforming method of the present invention, in the pipe expanding step, the outer peripheral length of the joint of the pipe expanding portion is set to be shorter than the outer peripheral length of the portion of the pipe expanding portion other than the joint. Therefore, even when the degree of pipe expansion is large in the pipe expanding step, the load acting on the joint is reduced. Therefore, while avoiding damage to the joint, it is possible to increase the degree of pipe expansion of the portion other than the joint of the pipe expanding portion.

According to the hydrofoam tubular member of the present invention, the outer peripheral length of the seam of the expanded pipe portion is set shorter than the outer peripheral length of the other parts of the expanded pipe portion other than the seam. Therefore, even when the degree of pipe expansion is large in the pipe expanding step, the load acting on the joint is reduced. Therefore, while avoiding damage to the joint, it is possible to increase the degree of pipe expansion of the portion of the pipe expanding portion other than the joint.

When the hydrofoam tubular member according to the present invention is applied to a structure such as a reinforcing member represented by a front side member, an external force acts along the axial direction of the hydrofoam tubular member. At this time, since the outer peripheral length of the joint is set to be shorter than the outer peripheral length of the other portion of the expanded portion other than the joint, the joint is deformed and absorbs the impact with priority over the other portion, and the important part It can also be expected to function as a crash bead that protects the human body.

[Brief description of drawings]

FIG. 1 is a perspective view of an element pipe before a hydroforming method according to a first embodiment.

FIG. 2 is a partial cross-sectional view of an element pipe before a hydroforming method according to the first embodiment.

FIG. 3 is a perspective view of a hydroform tubular member formed by a hydroform method according to the first embodiment.

FIG. 4 is a perspective view of a first protrusion of a mold used in the hydroforming method according to the first embodiment.

FIG. 5 is a perspective view of a second protrusion of the molding die used in the hydroforming method according to the first embodiment.

FIG. 6 is a cross-sectional view showing a state in which a raw pipe is arranged in a molding cavity of a molding die according to the first embodiment.

FIG. 7 is a cross-sectional view showing a state in which a raw pipe arranged in a molding cavity of a molding die is inflated according to the first embodiment.

FIG. 8 is a cross-sectional view showing a state in which the raw pipe arranged in the molding cavity of the molding die is further expanded according to the first embodiment.

FIG. 9 is a cross-sectional view of a pipe expanding portion of a hydrofoam tubular member according to the first embodiment.

10A is a cross-sectional view showing a state in which a groove of a hydrofoam tubular member is formed by the first projecting portion of the forming die according to the first embodiment, and FIG. FIG. 6 is a cross-sectional view of an expanded portion of a hydroform tubular member having a groove according to an example.

FIG. 11A is a cross-sectional view showing a state in which a chamfered portion of a hydrofoam tubular member is formed by the second protrusion of the molding die according to the first embodiment, and FIG. It is sectional drawing of the pipe expansion part of the hydroform cylindrical member which has a chamfered part according to 1 Example, (C) is an enlarged view of a chamfered part.

FIG. 12 is a perspective view of a hydroform tubular member formed by a hydroform method according to the second embodiment.

FIG. 13 is a perspective view of a hydroform tubular member formed by a hydroform method according to the third embodiment.

FIG. 14 is a cross-sectional view of a pipe expanding portion of a hydrofoam tubular member in which a radius of curvature of a corner region is set large according to the fourth embodiment.

FIG. 15 is a partial cross-sectional view of a raw pipe before forming by the hydroforming method according to the fifth embodiment.

FIG. 16 is a perspective view of a raw tube before being molded by the hydroforming method according to the sixth embodiment.

FIG. 17 is a perspective view of an element pipe before being formed by the hydroforming method according to the seventh embodiment.

FIG. 18 is a perspective view of an element pipe before it is formed by the hydroforming method according to the eighth embodiment.

FIG. 19 is a perspective view of a hydroform tubular member formed by a hydroform method according to the ninth embodiment.

FIG. 20 is a schematic configuration diagram in which a hydrofoam tubular member is applied to a front side member according to an application example.

[Explanation of symbols]

In the figure, 1 is a blank pipe, 11 is a first tubular member, 12 is a second tubular member, 13 is a third tubular member, 21 is a first seam, 22 is a second seam, 3 is a molding die, 4 Is a hydrofoam tubular member, 40 is a pipe expanding portion, 51 is a groove, 52 is a chamfered portion, and 7 is a front side member (hydrofoam tubular member).
Indicates.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hironori Iseki             Aishi, Tenno, Takaoka Shinmachi, Toyota City, Aichi Prefecture             Takaoka Co., Ltd. (72) Inventor Hideaki Ikezawa             Aishi, Tenno, Takaoka Shinmachi, Toyota City, Aichi Prefecture             Takaoka Co., Ltd. (72) Inventor Kiyoto Kondo             Aishi, Tenno, Takaoka Shinmachi, Toyota City, Aichi Prefecture             Takaoka Co., Ltd. (72) Inventor Toshiyuki Takasago             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Hiroto Usui             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Masaki Tanzawa             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Koji Makino             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Yoshihiro Asasa             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Hiroaki Shigerou             5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Corporation             Ceremony Company Nagoya Steel Works (72) Inventor Koichi Sato             5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Corporation             Ceremony Company Nagoya Steel Works (72) Inventor Tomoyoshi Tomasa             5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Corporation             Ceremony Company Nagoya Steel Works

Claims (17)

[Claims] 1. A joining step of forming a joint pipe by joining axial end faces of at least two tubular members in series to form a joint, and a joining pipe in a cavity of a molding die. By arranging step of arranging, by increasing the internal pressure of the hollow chamber of the raw pipe,
In the hydroforming method for expanding the peripheral wall of at least the portion having the seam of the raw pipe and bringing it into contact with the cavity mold surface of the molding die to form a pipe expanding portion, the pipe expanding step includes: A hydroforming method, comprising an operation of setting an outer peripheral length of the pipe expanding portion to be shorter than an outer peripheral length of a portion of the pipe expanding portion other than the seam. 2. The cavity die surface of the molding die according to claim 1, wherein the cavity die surface has a protrusion portion that protrudes toward the inside of the cavity, and the operation is performed by the protrusion portion of the cavity die surface of the molding die. A hydroforming method characterized in that it is performed by bringing the joints of the pipes into contact with each other. 3. The tubular member according to claim 1 or 2, wherein the tubular member is a first tubular member, a second tubular member joined in series to the first tubular member, and the second tubular member. And a third tubular member joined in series to the tubular member. 4. The hydroforming method according to claim 1, wherein the adjacent tubular members have different characteristics from each other. 5. The hydroforming method according to claim 4, wherein the characteristic is at least one of strength, hardness, plastic deformability, wall thickness, and composition. 6. The operation according to any one of claims 1 to 5, wherein the cross-sectional area of a joint portion of the pipe expanding portion is larger than that of a portion other than the joint of the pipe expanding portion. The hydroforming method is characterized in that it is performed so as to be small. 7. The hydro according to any one of claims 1 to 6, wherein the operation is performed by forming a chamfered portion in a corner region of a seam of the pipe expanding portion. Form method. 8. The operation according to any one of claims 1 to 6, wherein the radius of curvature of an arc defining a contour of a corner region of the joint of the pipe expanding portion A hydroforming method, which is performed so as to be larger than a radius of curvature of a circular arc that defines a contour of a corner region other than the seam. 9. The seam according to any one of claims 1 to 8, wherein a plurality of the seams are provided in the axial direction, and the outer peripheral length of at least one seam is different from the outer peripheral lengths of other seams. Hydroforming method characterized by being regarded as a value. 10. A hydroform tubular member formed by a hydroform method, which has a hollow chamber in which axial end surfaces of at least two tubular members are joined in series to form a joint, and the outer peripheral length of the joint is A hydroformed tubular member, which is set to be shorter than the outer peripheral length of the expanded portion other than the seam. 11. The tubular member according to claim 10,
A first tubular member, a second tubular member joined in series to the first tubular member, and a third tubular member joined in series to the second tubular member, Hydrofoam tubular member. 12. The method according to claim 10 or 11,
A hydroformed tubular member, wherein the adjacent tubular members have different characteristics. 13. The hydroformed tubular member according to claim 12, wherein the characteristic is at least one of strength, hardness, plastic deformability, wall thickness, and composition. 14. The hydroform according to any one of claims 10 to 13, wherein the cross-sectional area of the seam is set smaller than the cross-sectional area of a portion other than the seam. Cylindrical member. 15. The hydroformed tubular member according to claim 10, wherein a corner region of the joint has a chamfered portion. 16. The radius of curvature of an arc defining a contour of a corner area of the seam according to any one of claims 10 to 15, wherein a radius of curvature of an arc of the expanded pipe portion other than the seam. A hydroformed tubular member having a radius of curvature larger than that of an arc defining the contour of the partial region. 17. The seam according to any one of claims 10 to 16, wherein a plurality of the seams are provided in the axial direction, and an outer peripheral length of at least one seam is different from an outer peripheral length of another seam. A hydrofoam tubular member characterized by having a value.